In recent years, the technology called OpenFlow (OpenFlow) is proposed (refer to Non Patent Literatures 1 and 2). OpenFlow identifies communications as end-to-end flows, and performs path control, failure recovery, load distribution, and optimization on a per-flow basis. An OpenFlow switch specified in Non Patent Literature 2 includes a secure channel for communication with an OpenFlow controller. The OpenFlow switch operates according to a flow table in which appropriate adding or rewriting is instructed by the OpenFlow controller. In the flow table, a set of a matching condition (Match condition) to be matched against a packet header, flow statistics information (Counters), and instructions (Instructions) defining processing content is defined for each flow (refer to section “4.1 Flow Table” in Non Patent Literature 2).
When the Open Flow switch receives a packet, for example, the OpenFlow switch searches the flow table for an entry having a matching condition that matches header information of the received packet (refer to “4.3 Match Fields” in Non Patent Literature 2). When the entry that matches the received packet is found as a result of the search, the OpenFlow switch updates the flow statistics information (one or more Counters), and executes processing content (e.g., transmission of the packet from a specified port, flooding of the packet, discarding of the packet, or the like) described in the instruction field of the entry. On the other hand, when the entry that matches the received packet is not found as a result of the search, the OpenFlow switch transmits to the OpenFlow controller a request for setting the entry, or a request for determining the processing content of the received packet, through the secure channel. The OpenFlow switch receives the flow entry in which the processing content is defined, and then updates the flow table. In this manner, the OpenFlow switch performs packet forwarding by using the entry stored in the flow table as a processing rule.
Patent Literature 1 discloses an invention in which physical ports belonging to a link aggregation group are also to be managed by an OpenFlow controller. A user can thereby be made to arbitrarily control the physical port of an output destination, without depending on a sorting algorithm or the like inside an apparatus including the physical ports belonging to the link aggregation group.    PATENT LITERATURE 1:    JP Patent Kokai Publication No. JP2011-160171A    NON-PATENT LITERATURE 1:    Nick McKeown and seven other authors, “OpenFlow: Enabling Innovation in Campus Networks,” [online], [Searched on Jan. 11, 2012], Internet <URL: http://www.openflow.org/documents/openflow-wp-latest.pdf>.    [NON-PATENT LITERATURE 2]    “OpenFlow Switch Specification,” Version 1.1.0 Implemented (Wire Protocol 0x02), [online] [Searched on Jan. 11, 2012], Internet <URL: http://www.openflow.org/documents/openflow-spec-v1.1.0.pdf>.